The present disclosure generally relates to a fluid tank, such as a fuel tank, for a motor vehicle. More particularly, the present disclosure relates to a floating absorber assembly disposed in a fuel tank for reducing fuel slosh noise.
Sloshing noises that originate inside a fluid tank of a motor vehicle, such as a fuel tank, are generally due to the movement of liquid (e.g., fuel) that occurs during driving. In a vehicle's fuel tank, this sloshing noise can sometimes be heard inside the vehicle's passenger cabin, particularly at certain critical fuel volumes, and is considered a nuisance.
Historically, vehicle fuel tanks were made of steel. Noise or fuel slosh reducing baffles, including vertically-oriented absorbers, are more easily incorporated into steel fuel tanks for purposes of inhibiting the formation of waves within the fuel tank thereby reducing or eliminating noise or fuel slosh within the tank. More recently, many vehicle fuel tanks have been made of plastic, particularly in the U.S. where plastic fuel tanks are mandated. The incorporation of baffles or absorbers within plastic fuel tanks, particularly blow-molded plastic tanks, is difficult due to manufacturability problems and reduced fuel volume concerns.
Nonetheless, many dampener or baffle elements of various designs have been employed in the fuel tank in an attempt to prevent or reduce fuel sloshing noises. For example, it is known to locate inside a fuel tank dampener elements that float on the fuel surface. These dampener elements have a freely floating element whose surface is equipped with a dampening material, for example, a knitted fabric that has open pores. These dampener elements are provided for obstructing waves and currents in the tank in an effort to act directly as noise dampeners.
It is also known to locate at the interior walls of the fuel tank baffle elements to cause a reduction of the energy of the impinging fuel waves and thereby reduce impact noise. One such baffle design includes a corrugated plastic sheet molded with numerous slits which, when expanded, form meshes that serve as voids to entrap air and dissipate the energy of the fuel waves. In another design, the baffle element includes a sheet made from a large number of synthetic resin or plastic fibers that are mixed and entangled with one another, forming numerous energy dissipating voids. In yet another design, the dampener consists of a three-dimensional structured plastic insert whose structure forms small fuel wave calming chambers.
As indicated previously, at certain critical fuel volumes, particularly at a low fuel volume, not only does the amplitude of the waves causing the sloshing noise increase, but the resonance volume in the fuel tank also increases. This can cause the sloshing noise to become particularly loud. Baffles which are attached as impact elements at interior walls would have to cover nearly the entire fuel tank surface to have any chance of being effective. This approach is cumbersome, work-intensive and expensive, especially inside a plastic fuel tank where the only access to the interior of the tank is typically through a single opening for the fuel pump. Free floating dampener elements have a less complicated design and can be accommodated in fuel tanks with varying shapes if necessary. However, they can require a relatively large amount of space to be effective, which unnecessarily restricts the filling capacity of the fuel tank. In any case, there is a need for an improved absorber assembly for a fuel tank for reducing fuel slosh noise at critical fuel volumes.